Delhi's wettest July in years produced its worst air quality in seven

Delhi passed through a contradictory July. Average air quality across the first 30 days was 119, the highest monthly average for the month since 2019, when it stood at 134. In the same month the city recorded a rainfall surplus of 26 per cent at its base station and the first day classified 'good' on the national index in nine years. Both statements are true and neither cancels the other.

1. 1.119 — average AQI for July 2026, against 78 in July 2025 and 134 in July 2019.
2. 2.48 — the AQI on the month's one 'good' day, the lowest daily minimum recorded in a July since 2017.
3. 3.261 — the month's peak daily AQI, the highest July maximum in five years.
4. 4.15 moderate, 12 satisfactory, 2 poor, 1 good, 0 very poor — the month's day-count.
5. 5.254.7 mm against a 201.9 mm normal — July rainfall at Safdarjung.

Rain is not the same as washout

The instinct after a wet month is that the air must have cleared, and the statistics explain why it did not. Rainfall was concentrated. Skymet Weather's Mahesh Palawat attributed the above-normal total with below-normal rainy-day count to an unusually long break in the monsoon — around 10 to 11 days where a break normally runs five to six — with a few spells that were particularly intense at either end of the month.

That is a different mechanism from sustained light rain. A long break means long stretches of fine-weather subsidence, inversion conditions and dust, followed by short bursts that clear the air briefly and then leave the surface exposed again. Annual rainfall totals reward the month; daily air quality does not.

• Safdarjung: 254.7 mm in July against a 201.9 mm normal, an excess of 26%.
• The Ridge: 285.5 mm against 188.5 mm, an excess of 51% — the largest surplus among major stations.
• Lodhi Road: 274.4 mm against 201.9 mm, an excess of 36%.
• Ayanagar: 210.1 mm against 178.5 mm, an excess of 18%.
• Palam: 179.1 mm against 198.2 mm — a deficit of 10%, the one major station below normal.

Heat ran alongside. The city recorded its warmest July in two years on both measures, with an average maximum of 35.4 degrees Celsius and an average minimum of 27.7 — last exceeded together in 2024, at 35.9 and 27.8. Heat and stagnant air are the same problem viewed from two directions, and neither was relieved by a surplus of rain that arrived in the wrong places at the wrong times.

The seasonal position offers the only genuine comfort, and it is a modest one. Since the monsoon began, Safdarjung has recorded 296.5 mm against a seasonal normal of 276 mm — a surplus of 7 per cent. Delhi enters August slightly ahead on the season and behind on the air, and on the July evidence those two facts are not in contradiction.